Federal investigators join hunt for deadly heroin in Pennsylvania

Federal drug investigators have joined Pennsylvania officials' effort to find the source of a deadly batch of heroin that has killed 22 people in the western part of the state during the past two weeks.

The Pennsylvania attorney general's office, federal Drug Enforcement Administration and local law-enforcement authorities have been on high alert because the heroin involved in some deaths has contained fentanyl, a synthetic opiate often used during surgery that has played a role in other outbreaks of heroin overdoses.

Kathleen Kane, the state attorney general, said investigators have made progress following several credible tips. She declined to provide details but said the investigation would follow dual paths: Heroin in Pennsylvania is often traced back to Mexico, while illegal fentanyl produced by a chemist is typically harder to track, Ms. Kane said.

"We do have a good idea where it's coming from," she said of the drug mix implicated in the deaths. "We're trying to find the source and get them off the street before there are any more deaths."